Mars 8, the only Soviet/Russian lunar or planetary probe in twelve years (1988 to 2000), was an ambitious mission to investigate the evolution of the Martian atmosphere, its surface, and its interior.

The entire spacecraft comprised an orbiter, two small autonomous stations, and two independent penetrators. The three-axis stabilized orbiter carried two platforms for pointing several optical instruments for studying the Martian surface and atmosphere.

After an initial period in low orbit lasting three to four weeks acting as a relay to the landers, the orbiter would have spent approximately two Earth years in a 250 x 18,000-kilometer orbit mapping Mars. The orbiter would have released the two small autonomous stations four to five days before entering orbit.

The small stations would have landed on the Martian surface, cushioned by an inflatable shell that was to split open after landing. The stations were to have transmitted data daily (initially) and then every three days for about 20 minutes each session. The stations would have studied soil characteristics and taken photos on the surface.

The two 75-kilogram (each) penetrators, meanwhile, would have impacted the Martian surface at a speed of 76 meters per second to reach about 6 to 8 meters in depth. The orbiter would have released them after entering Martian orbit (between seven and twenty-eight days after entering orbit). During the mission's one-year lifetime, the penetrators would have served as nodes of a seismic network.

The Proton-K launch vehicle successfully delivered the payload to Earth orbit (after the first firing of the Blok D-2 upper stage). At that point, the Blok D-2 was to fire once again to place Mars 8 into an elliptical orbit, after which the Fregat propulsion module would have sent the spacecraft on a Martian encounter trajectory. The Blok D-2 engine, however, shut down prematurely after only 20 seconds as a result of a command from the payload, thus putting its precious payload into an incorrect orbit of 145.7 x 171.1 kilometers.

Mars 8 and its Fregat module then automatically separated from the Blok D-2. The latter seems to have fired (as planned earlier), placing Mars 8 in an 87 x 1,500-kilometer orbit that deposited the planetary probe in Earth's atmosphere.

Reports at the time suggested that debris from Mars 8 may have fallen in Chile or Bolivia, contaminating areas with its plutonium power source. Mars 8 was scheduled to arrive in Mars orbit on 23 September 1997.

Key Dates

16 Nov 1996: Launch (20:48:53 UT)

Status: Unsuccessful

Fast Facts

A malfunction during booster firing to send it to Mars marooned the spacecraft in Earth orbit. It re-entered Earth's atmosphere after three orbits.

At 6,200 kg, Mars 8 was the heaviest interplanetary probe and the most ambitious Mars mission of its time.